Respectfully speaking, there are thousands of people everyday who are bullied, harassed, victimized, abused, shot at, stabbed, bludgeoned, raped or murdered either because they were or were not in the right place at the right time.
The significance of this incident is that this was a peaceful demonstration against government policies, against tyrants who've oppressed their own citizens for decades, and in one defiant moment of selflessness, a lone student stood against an army of military vehicles equipped to decimate towns to slow them down and keep them from chasing down and killing countless of other protesters.
20 years ago isn't a lifetime ago... maybe 200 years. This incident is as historically significant as the assassination of Martin Luther King, Jr. or the attack of the Soviet Army on the people of Afghanistan or the brutality of the Somalian pirates who take hostages and murder the innocent. These events are important because our children and our spouses, our friends and family who were too young to witness or understand these events need to be taught the reasons why they happened. Without prevention, genocides occur; whole populations of people have been rounded up and shipped around or have been butchered because of their ethnicity and beliefs... Native Americans, African, Arabs, Asians, Polish. Slovene and Jews have suffered at the hands of tyrants. It's important to remember these events and teach our children these events so that they understand the danger in complacency and racism and to take pride in their own ethnicity as well as embrace and understand the ethnicity and beliefs of others.
On September 11, 2001 the United States became the victim of terrorism by murderers who were acting on blind faith. The people of the United States reacted violently and angrily against the forces who were training these men because the nation had become lazy and let our guard down against those who prey on the innocent.
Shielding our children from the harsh realities of war is one thing, they should not be burdened to know the inhumanity that people are subjected to in times of war. However, children need to be educated as to the reasons that cause wars to occur and have a good sense of moral reasoning to discriminate what the difference is between a just cause and an unjust conflict.
So I guess it's typical western behavior to forget that such atrocities occur and to criticize or ridicule those who speak about the past because we're not focused on the atrocities in the present... or perhaps it's merely the typical behavior of those who enjoy the safety and protection that their government affords them. I'd say it's more likely that the truly ignorant don't understand that there are still places in the world where media loudmouths like Reverend Al Sharpton and Rush Limbaugh would be imprisoned for criticizing their government and people like ourselves wouldn't be reading this because it would be suppressed as well.
Keep that in mind the next time you pass a veteran who can't find a job and is asking for help on the street, even though his government promised to support him when he came home from service overseas in the name of liberty and fought a just cause. Ask him or her how they served and what happened, and listen to their stories. Even if you don't understand their anger, try to understand their frustration.
The last reason that anyone wants to hear is "Because said nothing and I did nothing about it."

As much as we can whine and bitch about how President George Bush, Sr. got us into a war with Iraq, and his son pushed American troops back into Iraq, and it seems at times that America is at war with itself, it's important to remember that our tanks and soldiers aren't pointing their weapons at their own citizens and in America, and joining the military is a voluntary decision in America. Also being Pro-life is a CHOICE, not a government directive. We should also bear in mind that 40 years ago in America, a bunch of students marched on university campuses and rioted and caused destruction over our military actions in Vietnam... a stark contrast to a peaceful demonstration 20 years ago in Tienanmen Square where innocent civilians were butchered by their own government. Unfortunately, many of us don't appreciate our personal liberties or value or freedom until we witness others having it stripped from them.